1. Field of the Invention
The present invention relates to the field of nuclear measurement of densities, levels and profiles of liquids such as oil and water which have been extracted from the ground either through land drilling or offshore drilling.
2. Description of the Prior Art
In general, conventional methods to determine the percentage of drill results which is oil is known. The prior art sensors are placed in a single longitudinal array, so if a sensor malfunctions, the entire sensor array must be removed from the measuring tank and the defective sensor replaced. This results in downtime as the system must be shut down to replace the malfunctioning sensor in the sensor array. The tank must also be emptied to repair the malfunctioning sensor.
In a profiler system, multiple source and collector systems are placed in a vertical array so material is examined at specified heights within the liquid.
Photomultiplier tubes have many undesirable characteristics when used in systems designed to measure potentially explosive components of oil. These include:                a. High voltage potentials in the range of 1 KV are required to bias the PMT. These can spark explosions and must be carefully contained so they do not penetrate the fluid they are measuring.        b. Generate considerable heat which requires an external cooling system. Usually, cooled water is pumped through water jackets surrounding the part.        c. Electrical performance is degraded over time and temperature, again requiring external cooling equipment and frequent re-calibration.        d. PMT's are sensitive to stray magnetic fields often needing magnetic shielding to avoid spurious measurement errors.        e. Being constructed from delicate mechanical components and housed in glass packaging makes PMTs very fragile.        f. Performance from unit to unit is highly variable requiring careful and time consuming “in system” calibration. This usually requires the system to be shut down resulting in significant production dead time.        
There is a significant need for an improvement in the prior art systems.